Sanford Weill is to step down by next year as chief executive of Citigroup, the US banking giant has said.

Mr Weill has been heavily criticised for the bank's alleged past failings in connection with the Enron scandal and recommendations to buy tech and dot.com shares.

The bank paid $400m - more than any other bank - as part of a global settlement of the stock research case. And it set aside much more to cover potential costs arising from the bank's alleged role in helping Enron misrepresent its finances.

Mr Weill was earlier this year forced to withdraw his candidature for a seat on the board of the New York Stock Exchange representing investors, following objections from the New York attorney general.

Aged 70, Mr Weill will remain Citigroup chairman until 2006.

He will be replaced as chief executive by Charles Prince, 53, who has run Citigroup's global corporate and investment bank since September.